The issue with four gallon pots is going to be the amount of water in the soil. If some parts stay to wet anaerobic bacteria can take hold and increase the pH leading way to rot and other nutrient deficiencies. A fan, proper temps and water the right amount every three days will help. Ph goes up not down after we feed the plants. some things like Mg combine with N under a pH of 5.8. Cannabis like 5.9 to 6.1 though when watering with foxfarm nutrients the intital ph of the batch will be lower. Dont adjust it it will raise on its own and have different things beneficial to the plant happen along the way. If watering every three days I would not add more then 300ppm per feeding so the high tds does not wipe out the microbs in the soil.